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ch09-02: ? may be used with Result or Option #1852

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ch09-02: ? may be used with Result or Option #1852

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10 changes: 5 additions & 5 deletions src/ch09-02-recoverable-errors-with-result.md
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Expand Up @@ -470,13 +470,13 @@ and returns it. Of course, using `fs::read_to_string` doesn’t give us the
opportunity to explain all the error handling, so we did it the longer way
first.

#### The `?` Operator Can Only Be Used in Functions That Return `Result`
#### The `?` Operator Can Only Be Used in Functions That Return `Result` or `Option`

The `?` operator can only be used in functions that have a return type of
`Result`, because it is defined to work in the same way as the `match`
expression we defined in Listing 9-6. The part of the `match` that requires a
return type of `Result` is `return Err(e)`, so the return type of the function
must be a `Result` to be compatible with this `return`.
`Result` or `Option`, because it is defined to work in the same way as the
`match` expression we defined in Listing 9-6. The part of the `match` that
requires a return type of `Result` is `return Err(e)`, so the return type of
the function must be a `Result` to be compatible with this `return`.

Let’s look at what happens if we use the `?` operator in the `main` function,
which you’ll recall has a return type of `()`:
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